The present invention relates to sensors for partial discharge sensing. In particular, the invention relates to RF current transformer sensors used for detecting partial discharges in power cables.
Partial discharge sensing can be used to assess the condition of power cables. More particularly, partial discharge sensing can be used to detect deterioration of insulation of power cables by detecting high frequency currents that are created by small gaps, voids or other deterioration in power cable insulation.
Typically, a partial discharge sensing system includes a partial discharge sensor, a spectrum analyzer, and a signal cable for carrying electrical signals between the sensor and the spectrum analyzer. In order to conduct an online partial discharge test, an operator secures the sensor at a test location on a “live” power cable (i.e., one with electrical current flowing through it). Then, the operator manually conducts a partial discharge test using the spectrum analyzer.
Some partial discharge sensors are split core RF current transformer sensors. These sensors are clam-shaped and hinged, with a generally circular central opening formed when the sensor is in a closed position. In use, these sensors are closed around the power cable to be tested in order to conduct tests. Operators must touch these split core sensors in order to secure them to the power cable. With online testing, the power cable is energized or “live”. Therefore, the operator's hands must come in close proximity to the “live” power cable in order to secure the split core sensor to it. This presents a safety hazard to operators, who risk electrical shock, electrocution, and other serious injury, as the power cables can carry current at a high voltage (e.g., 15,000 volts).